The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Removal of oil, solid phases, scum, and/or flocculated materials from aqueous fluids has been practiced in numerous industries for several decades, and depending on the specific contaminant, suitable devices can be chosen. For example, centrifugal separation or filtration is a relatively effective and fast method of separating fairly high concentrations of large solid particles from a liquid, however, has limited use where the particle size and/or concentration are relatively low. Moreover, especially where the volume of treated fluid is relatively large, centrifugal separation often becomes impractical due to the required rotor size and energy consumption.
Where the solid material has a lower density than the solvent (e.g., oil sludge, scum, coagulated, or flocculated materials) solids can often be easily removed without significant mechanical intervention in settling or holding tanks. However, where the effluent volume is relatively large and/or the density difference is relatively small, the required volumes for the settling or holding tanks and the time needed for separation would be impractical under most circumstances. To improve at least some aspects of separation, a skim tank imparting toroidal motion in a mixed phase and a conical weir have been described in WO 2008/137006. While such systems and methods improve certain parameters of operation, various drawbacks still remain, including issues with high dissolved organic solids, emulsions, etc. All publications identified herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
Separation of mixtures of undesirable components from water is further compounded by the presence of contaminants with various and distinct physicochemical parameters. For example, SAGD produced water has considerable quantities of dissolved organic compounds often in tight emulsions in addition to silica, inerts, and numerous organic hydrocarbonaceous compounds at high pH (e.g., pH>8.5). GB 2489815 describes a system of heating produced water to a degree that reduces hydrocarbon content in a distillation-type manner. However, such process is energy demanding and typically fails to reduce emulsified components and other small contaminants.
Still further, SAGD produced water will also have in many instances a high scaling index, rendering such water unsuitable for substantially all downstream equipment as untreated SAGD produced water tends to deposit oily scale on all wetted surfaces, even filter media. Because SAGD operation requires substantial quantities of water for steam generation and produces significant quantities of produced water, recycling water has become imperative. Indeed, some environmental regulations require up to 90% recovery of recycled water for steam production for enhanced oil recovery. Unfortunately, treated produced water is still often unsuitable for OTSG. In an effort to reduce difficulties with scaling in OTSG, produced water is treated by raising the pH to a level that significantly increases silica solubility and breaks emulsions. So treated water is then further processed to reduce water hardness prior to feeding into a steam generator to form intermediate quality steam as described in WO2013/049378. While such system provide several advantages over other known plants and methods, the quality of the treated water may still be problematic, especially where tight emulsions and numerous other contaminants are present.
Therefore, while numerous methods of mixed-phase separation are known in the art, all or almost all of them suffer from one or more disadvantages. Consequently, there is still a need to provide improved configurations and methods to improve mixed-phase separation, especially where colloidal clay/silica etc. are emulsified in a liquid.